The present invention relates to an original-holding cover for use in association with an image formation device such as a copying machine, an original reader and so on.
In image formation devices generally, it is common to maintain an original in intimate contact with an original platen by means of a device such that an original-holding cover is rotatably linked to the original platen
Where such an original-holding cover comprises a single flat plate, the cover is capable of assuring a close contact of the original all over its surface with the platen when the original is sufficiently thin. However, when the original is thick, e.g. in the case of a book, such an original-holding cover exerts its pressing force only partially, failing to assure an intimate contact of the entire surface of the original with the platen
To solve this problem, there has been provided an original-holding cover comprising a base part and an original-holding part which are rotatably interconnected. Furthermore, in order to prevent the base part from rotating in association with the movement of the original-holding part when only the original-holding part is used by opening and closing, original-holding covers each having either of the following arrangements (1) or (2), have been provided
(1) Either of the base part or the platen is provided with a magnet and the other with a magnetic element, at predetermined positions (Publication for unexamined Japanese Utility Model Application No. 112248/1984).
(2) The platen is provided with an engaging means that engages with the original-holding part at a predetermined position thereby to control the angle of rotation when the original-holding part only is opened (Publication for unexamnied Japanese Utility Model Applications No. 96559/1983 and No. 119447/1984).
Regarding the above original-holding cover of construction (1), since the attraction between the magnet and magnetic element controls the rotation of the base part, the rotation of the base part can be positively prevented when the original-holding part only is opened. Moreover, when a thick original is copied with use of this original-holding cover, the base part is rotated through a necessary angle with the abutment between the original-holding part and the original serving as a fulcrum, thereby to apply a pressing force to the entire surface of the original.
However, since this construction requires the installation of a magnet and a magnetic element, the structure becomes complicated and demands additional parts. Furthermore, setting of the attractive force between the magnet and magnetic element is difficult and the decrease in magnetic force due to aging results in a failure to control the rotation of the base part.
Regarding the aforesaid original-holding cover of construction (2), since the angle of rotation of the original-holding part itself is restricted by an engaging means provided on the platen, the rotation of the base part can be completely prevented.
Furthermore, with this original-holding cover, a thick original can be subjected to a pressing force over the entire surface by rotating the base par through a necessary angle with the abutment between the original-holding part and the original serving as a fulcrum.
However, in this latter construction, the platen and the original-holding part must be provided with mating elements at predetermined positions and this entails a complicated construction and demands additional parts. Furthermore, high accuracy is required in the positional relationship between the mating elements as well as in their size, and this deteriorates workability in mounting the original-holding cover on the platen.